5aSP17. Changes in voice-onset time in speakers with cochlear implants.

Voice-onset time (VOT) was measured for the English plosives in /C(open
aye)/ context spoken by three female and one male postlingually deafened
recipients of multi-channel (Ineraid) cochlear implants. Recordings were made
of their speech before activation of their speech processors and at intervals
after activation, extending over several years. Also measured were:
instantaneous oral airflow; sound pressure level; an indirect index of glottal
aperture; and average airflow during passage readings. Pre-implant, all four
speakers characteristically uttered plosives with too-short VOT, compared to
normative data. After activation of their processors, all four were relatively
accurate in identifying plosives with respect to voicing, and the three female
speakers lengthened VOT. The women also increased glottal aperture
post-activation. However, none of the women increased peak oral flow following
plosive release, possibly because of a countervailing decrease in subglottal
pressure: all three reduced SPL post-activation. Complementary results were
found for the male speaker: a decrease in inferred glottal aperture and an
increase in oral flow accompanied by an increase in SPL. Increases in glottal
aperture are expected to inhibit the onset of voicing in the plosives [K.
Stevens, Phonetica 34, 264--279 (1977)]. Consequently, some or all of the
observed increases in VOT with activation of the implant processors may be due
to ``postural'' adjustments of the larynx. [Work supported by N.I.D.C.D.]